Caught in the Lower-Middle: Socioeconomic Inequality and Midlife Well-Being Trajectories Across Historical Time

This research investigates socioeconomic disparities in midlife well-being trajectories across historical time by analyzing longitudinal patterns of life satisfaction, depressive symptoms, and loneliness across four U.S. socioeconomic strata (0–15%, 16–45%, 46–75%, and 76–100%; Rehkopf et al., 2025). Beyond mapping historical changes in well-being, this research examines whether the extent of heterogeneity in these trajectories—and the influence of key predictors such as marital status, obesity, out-of-pocket medical expenditure, and stressor exposure—remains consistent across historical cohorts. Additionally, we aim to assess whether these patterns replicate across other national contexts, namely Mexico, Europe (Austria, Belgium, Switzerland, Germany, Denmark, Spain, France, Greece, Italy, Netherlands, Sweden, Israel), and Asia (South Korea and China). We hypothesize that the U.S. will show historical declines in life satisfaction and historical increases in depressive symptoms and loneliness across birth cohorts (e.g., those born in the 1950s and 1960s will exhibit a worse pattern compared to those born in the 1930s and 1940s), particularly among the lower-middle SES group. Conversely, we hypothesize that historical improvements will be observed in each outcome of interest (i.e., declines in depressive symptoms and loneliness and increases in life satisfaction) across birth cohorts in Mexico, Europe, and Asia, and the distinction across SES groups will be less pronounced. We also hypothesize that the relative strength of predictor effects will change across historical time. Specifically, for more recent cohorts, the protective effect of marriage will diminish, while the negative impact of obesity, out-of-pocket-medical expenditure and stressor exposure will be amplified. We hypothesize that these historical differences in predictor effects will be more pronounced in the U.S. as compared to the other nations.